Effectiveness of the adjuvanted Sanofi/GSK (VidPrevtyn Beta) and Pfizer-BioNTech (Comirnaty Original/Omicron BA.4-5) bivalent vaccines against hospitalisation amongst adults aged 75 years and older in England, estimated using a test-negative case control study design.

BackgroundIn England, the Joint Committee for Vaccination and Immunisation recommended a spring 2023 booster programme for all adults aged 75 years and older and the immunosuppressed. The vaccines advised were the Sanofi/GSK AS03-adjuvanted monovalent beta variant (VidPrevtyn Beta) booster vaccine and the Pfizer-BioNTech mRNA (Comirnaty Original/Omicron BA.4-5) bivalent vaccine. This is the first time an adjuvanted COVID-19 vaccine has been administered as part of a UK COVID-19 vaccination programme. In clinical trials, the antibody levels generated by the Sanofi/GSK vaccine were comparable to levels generated by COVID-19 mRNA vaccines but to date there are no real-world data on the effectiveness or duration of protection of this vaccine. MethodsWe used a test-negative case-control study design to estimate the incremental vaccine effectiveness of the Sanofi/GSK and Pfizer bivalent BA.4-5 boosters against hospitalisation amongst those aged 75 years and older in England. The study period for tests contributing to all analyses was from 3rd April 2022 to 27th August 2023. Vaccine effectiveness was estimated relative to those who had received at least two doses prior to their spring booster, with their last dose being an autumn 2022 booster given at least 3 months prior. FindingsOverall, there were 14,174 eligible tests from hospitalised individuals aged 75 years and older, with 3,005 being cases and 11,169 being controls. Effectiveness against hospitalisation was highest in the period 9 to 13 days post vaccination for both manufacturers at about 50%; 43.6% (95% C.I.; 20.1 to 60.2%) and 56.4% (95% C.I; 25.8 to 74.4%) for Sanofi/GSK and Pfizer BA.4-5, respectively. There was some evidence of waning with a reduction to about 30% for both manufacturers 5-9 weeks post vaccination. InterpretationTogether, these results provide reassuring evidence that both the adjuvanted Sanofi/GSK and Pfizer BA.4-5 booster vaccines provided a good boost to protection against hospitalisation amongst adults aged 75 years and older. The finding that the adjuvanted vaccine targeting the now distant Beta strain had similar effectiveness to the mRNA vaccine targeting more closely matched Omicron sub-lineages BA.4-5 during a period of Omicron circulation may reflect improved protection due to the adjuvant in the Sanofi/GSK product. FundingNo external funding.